Blender game runs very slow
You can always tell what it jacking up a game by turning on FrameRate/Profile, an option under the "Game" tab.

In realtime, it will dynamically calculate how much time blender is spending on each part of the game, and you can see what is causing problems, and what could be beefed up without issues.



I'm going to go ahead and take a wild guess that your scene is slowed down by "Rasterizer" or the rendering process. Why is this? You used basic meshes, simple graphics, and easy shading. So what is causing this kink?

It's the lights! if each one of you trees has it's own separate light, thats a whole different set of the same graphics that blender has to calculate.

You were right, fortunately, that this can be fixed quite easily with texture baking.
First of all, you will need to pick a target image that you want to bake your texture to. Then, under the render tab, hit bake. Once the bake is done, save it and apply it as a shadeless texture. All of the light will be on the ground, just like it was being actively rendered, but blender will be muuuuch happier. And we all know, when blenders happy, so are you.

How do I bake a texture using Cycles bake?